Histoplasmosis 



573 



The micro-organism differs from the Leishman-Donovan body 

 of kala-azar in the form and arrangement of its chromatin nucleus 

 and in not possessing a chromatin rod. The distribution of the 

 parasite in the body is accomphshed by the invasion of the contiguous 

 endothelial cells of the smaller blood- and lymph-vessels and cap- 

 illaries, and by the infection of distant regions by the dislodgment of 

 infected endothelial cells and their transportation thither by the 



Fig. 226. — Histoplasma capsulatum. Mononuclear cells from the lung con- 

 taining many parasites (Samuel T. Darling ia "Journal of Experimental 

 Medicine"). 



blood- and lymph-stream. Thus the skin, intestinal, and pulmonary 

 nodules may be due to secondary distribution of the parasite. The 

 micro-organism apparently lives for a considerable period of time 

 in the tissues, because in the older areas of necrosis there are myriads 

 of parasites all staining well. 



The mode of infection and portal of entry are unknown. The 

 parasite has neither been cultivated nor transmitted by inoculation. 



Believing it to be a new parasite, Darling has suggested that it 

 be called Histoplasma capsulatum. 



